Abstract:

The research is carried out to verify and supplement the heredity of cocoon shell ratio, which may provide a theoretical basis for breeding purebred silkworm with high cocoon shell ratio. The strains Jingsong, Haoyue with high silk yield and Furong, Xianghui with moderate silk yield were used as parents to construct five generations of genetic population, and then the inheritance cocoon shell ratio was analyzed by the multi-generation joint analysis method. The results showed that gender effects of cocoon quality traits were very obvious and cocoon shell ratio of male was higher than that of female. Cocoon shell ratio of parents was significantly and positively related to the cocoon shell weight. The cocoon shell ratio of F₁ hybrids fell in between that of the parents. The cocoon shell ratio of the reciprocal crosses was higher than that of the orthogonal crosses. The frequency of cocoon shell ratio in backcross populations followed the bimodal distribution or skewed unimodal distribution. The heterosis rate of cocoon shell ratio ranged from -3.82% to 5.63%, which indicated that there was almost no heterosis. Therefore, high cocoon shell ratio is a dominant character with maternal inheritance, the inheritance of cocoon shell ratio is regulated by polygenes, and there are major genes in the inheritance system that may be located on sex chromosome.

Key words: Bombyx mori, Cocoon Shell Ratio, Genetic Analysis, Gender Effect, Dominant Inheritance, Major Gene